ath6kl: Don't advertise HT capability for incapable firmware

With firmwares which do not support rsn capability override
(ATH6KL_FW_CAPABILITY_RSN_CAP_OVERRIDE) from host would
cause 4-way handshake failure when HT cap is advertised.
To fix this, do not advertise HT cap with cfg80211 for
those fw.

kvalo: fix a checkpatch warning

Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>